Merge pull request #31560 from vespa-engine/balder/no-opportunism-if-single-term

Balder/no opportunism if single term

2 files changed, 15 insertions, 2 deletions

diff --git a/container-search/src/main/java/com/yahoo/search/searchers/OpportunisticWeakAndSearcher.java b/container-search/src/main/java/com/yahoo/search/searchers/OpportunisticWeakAndSearcher.java
index 2995b9e830e..c56b161edeb 100644
--- a/container-search/src/main/java/com/yahoo/search/searchers/OpportunisticWeakAndSearcher.java
+++ b/container-search/src/main/java/com/yahoo/search/searchers/OpportunisticWeakAndSearcher.java
@@ -18,6 +18,9 @@ import com.yahoo.search.searchchain.Execution;
 /**
  * Will opportunistically replace the WeakAND with an AND as it is faster.
  * If enough hits are returned all is good and we return. If not we fall back to the original query.
+ * It is default off, and is enabled with weakAnd.opportunistic.and=true.
+ * It can be tuned with weakAnd.opportunistic.factor. Higher value than 1 might increase quality, lower value will
+ * improve performance. Default is 1.0. This factor is multiplied with the heap size of the wand(default 100) as target hits.
  *
  * @author baldersheim
  */
@@ -52,7 +55,9 @@ public class OpportunisticWeakAndSearcher extends Searcher {
     // returns targetHits for the first WeakAndItem found, -1 if none found.
     static int targetHits(Item item) {
         if (!(item instanceof CompositeItem compositeItem)) return -1;
-        if (item instanceof WeakAndItem weakAndItem) return weakAndItem.getN();
+        if (item instanceof WeakAndItem weakAndItem) {
+            return (weakAndItem.getItemCount() >= 2) ? weakAndItem.getN() : -1;
+        }
         for (int i = 0; i < compositeItem.getItemCount(); i++) {
             int targetHits = targetHits(compositeItem.getItem(i));
             if (targetHits >= 0) return targetHits;
diff --git a/container-search/src/test/java/com/yahoo/search/searchers/OpportunisticWeakAndSearcherTestCase.java b/container-search/src/test/java/com/yahoo/search/searchers/OpportunisticWeakAndSearcherTestCase.java
index c099cf437f8..f41c74a4b8e 100644
--- a/container-search/src/test/java/com/yahoo/search/searchers/OpportunisticWeakAndSearcherTestCase.java
+++ b/container-search/src/test/java/com/yahoo/search/searchers/OpportunisticWeakAndSearcherTestCase.java
@@ -6,6 +6,7 @@ import com.yahoo.prelude.query.AndItem;
 import com.yahoo.prelude.query.CompositeItem;
 import com.yahoo.prelude.query.Item;
 import com.yahoo.prelude.query.OrItem;
+import com.yahoo.prelude.query.TrueItem;
 import com.yahoo.prelude.query.WeakAndItem;
 import com.yahoo.prelude.query.WordItem;
 import org.junit.jupiter.api.Test;
@@ -22,10 +23,17 @@ public class OpportunisticWeakAndSearcherTestCase {
         return root;
     }
 
+    private static CompositeItem addItem(CompositeItem composite, Item item) {
+        composite.addItem(item);
+        return composite;
+    }
+
     @Test
     public void requireThatWeakAndIsDetected() {
         assertEquals(-1, OpportunisticWeakAndSearcher.targetHits(new OrItem()));
-        assertEquals(33, OpportunisticWeakAndSearcher.targetHits(new WeakAndItem(33)));
+        assertEquals(-1, OpportunisticWeakAndSearcher.targetHits(new WeakAndItem(33)));
+        assertEquals(-1, OpportunisticWeakAndSearcher.targetHits(addItem(new WeakAndItem(33), new TrueItem())));
+        assertEquals(33, OpportunisticWeakAndSearcher.targetHits(addItem(addItem(new WeakAndItem(33), new TrueItem()), new TrueItem())));
         assertEquals(77, OpportunisticWeakAndSearcher.targetHits(buildQueryItem(new OrItem(), new WeakAndItem(77))));
         assertEquals(77, OpportunisticWeakAndSearcher.targetHits(buildQueryItem(new AndItem(), new WeakAndItem(77))));
         assertEquals(-1, OpportunisticWeakAndSearcher.targetHits(buildQueryItem(new OrItem(), new AndItem())));